Malfunction Indicator Lamp (MIL)
WARNING: This page is about a different car, the 2006 Suzuki Reno and 2006 Suzuki Forenza. However, it is still accessible from the selected car via links, so may be relevant.
The Malfunction Indicator Lamp (MIL) is required by On-Board Diagnostics (OBD II) that it illuminates under a strict set of guide lines.
Basically, the MIL is turned ON when the Powertrain Control Module (PCM)/Engine Control Module (ECM) detects a DTC that will impact the vehicle emissions.
The MIL is under the control of the Diagnostic Executive. The MIL will be turned ON if an emissions-related diagnostic test indicates a malfunction has occurred. It will stay on until the system or component passes the same test, for three consecutive trips, with no emissions related faults.